220 THE ORIGIN OF SPECIES 



migrate, it is the slaves which determine the migration, and actu- 

 ally carry their masters in their jaws. So utterly helpless are the 

 masters, that when Huber shut up thirty of them without a slave, 

 but with plenty of food which they liked best, and with their own 

 larvae and pupae to stimulate them to work, they did nothing ; they 

 could not even feed themselves, and many perished of hunger. Hu- 

 ber then introduced a single slave (F. fusca), and she instantly set 

 to work, fed and saved the survivors; made some cells and tended 

 the larvae, and put all to rights. What can be more extraordinary 

 than these well-ascertained facts? If we had not known of. any 

 other slave-making ant, it would have been hopeless to speculate 

 how so wonderful an instinct could have been perfected. 



Another species, Formica sanguinea, was likewise first discov- 

 ered by P. Huber to be a slave-making ant. This species is found 

 in the southern parts of England, and its habits have been at- 

 tended to by Mr. F. Smith, of the British Museum, to whom I 

 am much indebted for information on this and other subjects. 

 Although fully trusting to the statements of Huber and Mr. Smith, 

 I tried to approach the subject in a sceptical frame of mind, as any 

 one may well be excused for doubting the existence of so extraordi- 

 nary an instinct as that of making slaves. Hence, I will give the 

 observations which I made in some little detail. I opened fourteen 

 nests of F. sanguinea, and found a few slaves in all. Males and 

 fertile females of the slave species (F. fusca) are found only in 

 their own proper communities, and have never been observed in 

 the nests of F. sanguinea. The slaves are black and not above half 

 the size of their red masters, so that the contrast in their appear- 

 ance is great. When the nest is slightly disturbed, the slaves occa- 

 sionally come out, and like their masters are much agitated and 

 defend the nest: when the nest is much disturbed, and the larvae 

 and pupae are exposed, the slaves work energetically together with 

 their masters in carrying them away to a place of safety. Hence, 

 it is clear that the slaves feel quite at home. During the months of 

 June and July, on three successive years, I watched for many 

 hours several nests in Surrey and Sussex, and never saw a slave 

 either leave or enter a nest. As, during these months, the slaves 

 are very few in number, I thought that they might behave differ- 

 ently when more numerous; but Mr. Smith informs me that he 

 has watched the nests at various hours during May, June, and 

 August, both in Surrey and Hampshire, and has never seen the 

 slaves, though present in large numbers in August, either leave or 

 enter the nest. Hence, he considers them as strictly household 

 slaves. The masters, on the other hand, may be constantly seen 



